An Overview on Three-Parent Babies

Andy Chen

adorable-71031_1280We can all recall the time our high school biology teachers taught us the basics of the human reproduction system. The process starts when a sperm enters an egg, each containing one half of a set of DNA. Essentially, the 23 pairs of chromosomes we inherit from our parents is what makes all of us unique. However, recent scientific developments have allowed for something much more complex: three-parent babies.

In a diploid human cell, there is an organelle referred to as the “powerhouse of the cell” – the mitochondria. This organelle converts energy from food into ATP for our bodies to utilize. Yet, a fascinating note about the mitochondria is that we inherit all of our mitochondrial DNA from our mothers.

In the mitochondria, certain genetic mutations can arise, causing mitochondrial disease. These mutations can lead to devastating physical and cognitive disabilities, such as loss of skeletal muscle function, loss of hearing, seizures, and learning disabilities. According to, about 1 in every 4,000 people has mitochondrial disease.

Thus, in today’s world, women who have mitochondrial disease are provided with the option to undergo a treatment that will lessen the probability of spreading the mutation to their offspring called “mitochondrial replacement.” There are several techniques in which the replacement occurs; however, one of the main methods involves inserting the mother’s nucleus into a donor egg, which comprises of the healthy mitochondria. Then, sperm fertilization occurs with the mother’s nucleus in the donor egg. The result is a  baby that technically has three parents, which can be confirmed through genetic tests.

baby-17374_1920With this new evolution of genetic transferring, there is ought to be constant uproar and ethical backlash against this procedure. However, in terms of the scientific perspective, there is still not much that we know about the negative consequences. Since there are so few three-parent babies, scientists are unable to assess the impact of mitochondrial replacement in the long term. Yet, there have been some studies in regard to the procedure which warn about the rise of complex phenotypic traits and a mito-nuclear mismatch, which could lead to developmental problems such as infertility and cancer. With the reasoning behind how a donor’s mitochondrial DNA may not coexist well with the mother’s original mitochondrial DNA, this may explain such problems and also propel the point that we need more studies done.  

Ultimately, we do not know about any long-term complications mitochondrial replacement or three-parent babies may have. However, there have been estimates that show that in the United Kingdom alone, this genetic modification can affect anywhere from two to twenty families per year. Although it is fascinating to see three-parent babies, or even the inevitable rise of “designer babies,” it may become necessary to balance our implications on the scientific desires for benefits with a sense of ethics and caution.

Perhaps in the next hundred years or so, biology teachers will teach their students about this new and fascinating method of reproduction.

To learn more about three-parent in vitro fertilization, click here.

Editor: Summer Lee